1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to an image pickup device, and more particularly to, an image pickup device which can improve optical efficiency and packaging convenience, and a method of manufacturing the image pickup device.
2. Description of Related Art
FIG. 1 is a perspective view illustrating the outer appearance of a related art image pickup device, and FIG. 2 is a cross-sectional view illustrating the image pickup device of FIG. 1. In FIGS. 1 and 2, there is shown a related art complementary metal-oxide semiconductor (CMOS) type image pickup device.
Referring to FIGS. 1 and 2, the related art image pickup device 10 is mounted on a semiconductor substrate 1. Electrode pads formed in a peripheral circuit region adjacent to an image pickup region of the semiconductor substrate 1 and terminals of the semiconductor substrate 1 are electrically connected to one another via wires 2. After the image pickup device 10 has been mounted on the substrate 1, a module housing (not shown) may be securely mounted on the image pickup device or the substrate.
The image pickup device 10 includes a silicon semiconductor substrate 20, an interlayer insulating film layer 40 having a plurality of insulating layers, a color filter 50, and a lens layer having a plurality of microlenses 60, which are sequentially formed on top of one another. Formed on the silicon substrate 20 are image sensors or light-receiving portions corresponding to respective pixels. Light irradiated onto the top portion of the image pickup device 10 passes through the interlayer insulating film layer 40 and is then transferred to the image sensors 30 on the silicon substrate 20.
The image sensors 30 are buried in a top surface of the silicon substrate 20, and the interlayer insulating film layer 40 is formed on the top surface of the silicon substrate 20. The interlayer insulating film layer 40 is provided with multi-layered wiring layers 45, each of which is connected to a corresponding image sensor 30 so as to construct an electric circuit. As mentioned above, as the number of pixels of the image pickup device increases, the wiring intervals of the wiring layers 45 become narrow and the wiring layers 45 can be multi-layered. Also, as the wiring pitches are reduced and the wiring layers are multi-layered, the amount of light transmitted to the image sensors 30 decreases and the distance between the lens layer 60 and the image sensors 30 increases.
A consideration when manufacturing the image pickup device is to improve an optical sensitivity. A fill factor of the light-receiving portions may be increased in order to improve the optical sensitivity. However, the related art image pickup device 10 has a shortcoming in that the wiring layers 45 may intercept the incidence light and the amount of light transmitted to the image sensors and the optical sensitivity may decrease due to the shading effect of the wiring layers 45.
To increase the optical sensitivity, a maximum possible area of the light-receiving portion should be secured. To this end, it is necessary to design a structure in which the metallic wiring layers are disposed below the light-receiving portion. A back-illuminated image pickup device employing such a structure has been disclosed.
However, the back-illuminated image pickup device also includes a silicon semiconductor substrate, a plurality of interlayer insulating films having wiring layers buried therein, a color filter, and a lens layer having a plurality of microlenses, which are sequentially formed on top of each other. Unlike the related art image pickup device, in the back-illuminated image pickup device, the color filter, and the lens layer are formed over the top surface of the silicon substrate in such a manner as to be opposite to the interlayer insulating film layer
Further, in the back-illuminated image pickup device, the silicon substrate may be attached on a support substrate and then the silicon substrate may be ground sufficiently thin so as to expose the image sensors to the outside. Also a color filter or microlenses may be formed on the silicon substrate.
In the existing back-illuminated image pickup device, since the wiring layers are not formed in an optical path, the optical sensitivity of the image sensors can increase and an adverse effect of the narrowed pitches and the multi-layered structure of the wiring layers on the optical sensitivity can be eliminated. Nevertheless, the back-illuminated image pickup device still has a shortcoming in that it is difficult to form electrodes and electrically connect the electrodes with an external substrate. The related art image pickup device has a disadvantage in that the electrode pads can be electrically connected to the substrate via the wires, but a larger installation space in addition to the image pickup region must be secured so as to form the electrode pads as shown in FIG. 1.
Accordingly, an image pickup device which can improve optical efficiency and packaging convenience, and a method of manufacturing the image pickup device is required.